Holographic metasurface can project images with single-micron pixels

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Holographic technology is widely misunderstood, primarily because the word is used so differently by scientists and the general public. Most people, when they hear the word ‘hologram,’ think of an object projected into the world around them as though it were a physical object like any other; this tends to be the Star Trek interpretation. Then there are those slightly more informed individuals who envision a Tupac-style recording that only seems to occupy space in the physical world. But the real definition of a hologram makes them both more useful, and more diverse than all that.

A team of researchers at Purdue University has created a material that produces holograms just a fraction of a millimeter above its own surface — one that could revolutionize everything from computing to high-resolution display technology. The key innovation here is not really related to the fact that their image is a hologram, however, but rather to the amazing properties their hologram can maintain.

The Tupac hologram, which appeared at a Coachella performance, really put holography in the public eye.

Holography captures and records light not as a static picture but as a matrix of information, so all that information can be projected again later; a hologram can seem to be truly three-dimensional because all the original information is recorded, not just the portion associated with a particular frame or viewing angle.

However, far from recording the image, this team’s material bends light inward, creating a stable, compressed version of an image shone through it from below. This means their “metasurface” has the ability to display images with details smaller than the wavelength of the originating light. Using photons for computing would of course be faster than using electrons, but the physical wavelength of light has made miniaturization impossible past a certain point — until now.

Though it was holo-chess that first planted the seed for many people.

The “metasurface” that allows such behavior is an incredibly thin sheet of gold foil bent into V-shaped micro-antennas. As light shines through this foil, it’s bent and redirected such that it converges to a new perceived location about 10 microns in front of the foil. That’s a small enough distance that you wouldn’t notice it on your monitor, for instance. What you would notice, though, is a several thousand-times increase in its pixel density; when these researchers wrote the word “Purdue” in miniature, the smallest features of their message were just 1 micron across.

This ability to use light on a scale well below its own seeming physical threshold is exciting to say the least. It opens the door for optical controllers integrated into chips themselves, potentially increasing processing power greatly. It might not bring Tupac back to life, but this is one breakthrough that could still change the way we view imagery in future.